The prognostic significance of macrocytosis in patients with myelodysplastic neoplasms
Authors: Panagiotis T. Diamantopoulos, Elena Solomou, Argiris Symeonidis, Vasiliki Pappa, Ioannis Kotsianidis, Athanasios Galanopoulos, Charalampos Pontikoglou, Achilles Anagnostopoulos, George Vassilopoulos, Panagiotis Zikos, Eleftheria Hatzimichael, Maria Papaioannou, Aekaterini Megalakaki, Theodoros Vassilakopoulos, Maria Dimou, Dimitrios Tsokanas, Menelaos‐Konstantinos Papoutselis, Sotirios Papageorgiou, Alexandra Kourakli, Helen Papadaki, Panayiotis Panayiotidis, Nora‐Athina Viniou
Journal: American Journal of Hematology (2023)

Accurate risk stratification of myelodysplastic neoplasms (MDS) is a key feature of treatment selection and predicts overall survival (OS). Taking into consideration several disease and patient-related characteristics, various prognostic scoring systems have been formulated. On the other hand, the elevated mean corpuscular volume (MCV) of the erythrocytes [macrocytosis, defined as an MCV over 100 femtolitres (fL)] is a classical feature of MDS and is considered a marker of dysplasia in patients with anemia and no other identifiable causes of macrocytosis, while it has been even used in a scoring system to establish the probability of MDS.1 Nonetheless, macrocytes can be classically found in patients with megaloblastic anemia, hypothyroidism, alcohol abuse, liver disease, and other bone marrow failure syndromes. The prevalence of macrocytosis in patients with MDS is considered high but has never been accurately estimated in large cohorts and its pathophysiological and prognostic roles have not been thoroughly evaluated. In the present study we investigated the prognostic role of macrocytosis in patients with MDS registered in the Hellenic 5-azacytidine Registry which is part of the Hellenic (Greek) National Registry of Myelodysplastic and Hypoplastic Syndromes comprising patients from 28 centers meeting the 2008/2016 World Health Organization criteria for MDS. The study was approved by the Hellenic Society of Hematology. The patients were stratified per the International Prognostic Scoring System (IPSS)2 and the revised IPSS (IPSS-R).3 The main hematologic variables, including MCV, were recorded at diagnosis and before any therapeutic interventions (such as red blood cell transfusions or erythropoiesis stimulating agent administration). Macrocytosis was defined as an MCV over 100 fL. Patients with an MCV lower than 80 fL as well as patients with a serum ferritin level suggestive of iron deficiency (<30 ng/mL) were excluded from the analysis, as well as patients with beta thalassemia trait which is a common disorder in Greece4 and megaloblastic anemia due to B12 vitamin or folate deficiency. The Pearson chi-square test, the independent-samples Mann–Whitney U test, and Kaplan–Meier analysis were used appropriately. Multivariate Cox regression models were built to assess association between categorical variables and the relative risk for death. The level of significance was set at a probability value lower than 5% (2-sided p < .05). The study comprised 833 patients, 73 of whom were excluded from the analysis due to a low MCV (N = 67, corresponding to 8.1% of the whole cohort, a rate compatible with the prevalence of beta thalassemia trait in Greece)4 or low ferritin levels (N = 6). The main characteristics of the final population of 760 patients are shown in Table S1. Macrocytosis was identified in 257 (33.8%) patients at diagnosis. As shown in Table S2, among the baseline characteristics of the patients, macrocytosis correlated only with higher platelet counts (123 × 109/L vs. 100 × 109/L for those without macrocytosis, p = .007). The median time from diagnosis to treatment initiation with 5-azacytidine was significantly shorter in patients without macrocytosis (3.2 months vs. 5.7 months for patients with macrocytosis; p = .015). Macrocytosis was correlated with an increased OS (median OS of 44.1 months vs. 33.5 months for those without macrocytosis, p = .002, Figure 1A), while there was a non-significant trend for lower acute myeloid leukemia (AML) transformation rate in patients with macrocytosis (22.7 months vs. 17.5 months for those without macrocytosis; p = .126).Multivariate analysis showed that macrocytosis was an independent predictor of a longer OS when tested against IPSS-risk or thrombocytopenia (Table S3). After stratification of the severity of macrocytosis (MCV, 100–110 fL vs. >110 fL) it was found that it did not have an impact on OS, or AML transformation rate. In lower-risk patients (N = 385), macrocytosis was identified in 128 (33.2%) and correlated with the absence of thrombocytopenia (p = .013), higher neutrophil counts (2.13 × 109/L vs. 1.81 × 109/L for patients without macrocytosis, p = .015), and a lower bone marrow blast percentage (3.0% vs. 4.5% for patients without macrocytosis, p = .001). Finally, it correlated with a longer OS (60.6 months vs. 47.4 months for patients without macrocytosis, p = .008, Figure 1B) and a longer time interval between diagnosis and 5-azacytidine initiation (16.8 months vs. only 7.2 months for those without macrocytosis, p ≤ .0001). Macrocytosis retained once again its statistical significance as a prognostic factor of OS when tested against neutropenia, low bone marrow blast count (≤1 vs. >1), and the IPSS risk (Table S3). In patients with higher risk MDS (N = 375), macrocytosis was identified in 129 (34.4%) and was not correlated with any of the baseline variables. Nevertheless, higher risk MDS patients with macrocytosis had longer OS than patients without macrocytosis (32.4 months vs. 23.0 months, p = .044, Figure 1C) and a longer time to AML transformation (15.7 months vs. 14.2 months for those without macrocytosis; p = .013). In patients with complex karyotype (n = 107), macrocytosis was present in 34 (31.8%) patients and was not correlated with any of the baseline variables, but it was once again correlated with a longer OS (28.7 months vs. 16.1 months for those without macrocytosis, p = .001, Figure 1D), although it was not correlated with the diagnosis-to-treatment time interval (p = .843). This survival correlation was independent of the IPSS (Table S3). In patients with a poor karyotype per the IPSS (n = 146), no correlations with any of the tested variables were identified, except for OS (27.3 months in macrocytic vs. 16.1 months in non-macrocytic patients, p = .006). Details on the cytogenetics of the patients are presented in Table S4. Regarding response to treatment with 5-azacytidine, patients with macrocytosis had a response rate (including complete, remission, partial remission, and hematologic improvement per the International Working Group response criteria for MDS) of 56.8%, while patients without macrocytosis had a response rate of 46.2% (p = .026). Macrocytosis is a classically described feature of MDS reflecting dyserythropoiesis and a lower number of mitotic divisions during the maturation process of the early erythropoietic cells. Although macrocytosis has been repeatedly reported as a prominent feature of patients with MDS, no quantification of this correlation has been attempted so far in the context of a study. Here we establish for the first time the rate of macrocytosis in a large cohort of patients with MDS (33.8%). This rate, although significant, does not reflect the prevailing idea that macrocytosis is a universal feature of MDS. In this cohort, there was a clear lack of correlation of macrocytosis with other features defining prognosis, such as the IPSS score and cytopenias except for the platelet count. Platelets along with red blood cells arise from the same progenitor cell. Because macrocytosis may reflect the asynchronous cytoplasm and nucleus maturation when dysplasia is present, the increased platelet count associated with macrocytosis observed in this study could be explained by the effort of this progenitor cell to overcome dysplasia and the increased cell turnover leading to increased bone marrow cellularity. An analogous process drives iron deficiency anemia-associated thrombocytosis. Interestingly, macrocytosis was not correlated with the severity of anemia or the need for transfusions, highlighting once again its independent prognostic nature, but it was correlated with a shorter time interval from diagnosis to treatment initiation, as well as a higher OS in the whole cohort, but also in both lower and higher risk patients. This correlation with survival was found to be independent of the IPSS categorization, highlighting macrocytosis as a strong independent factor of a better prognosis in patients with MDS, especially in lower risk patients, indicating which of them will progress and will have to be treated with a hypomethylating agent. These results consort with the results of a study on 321 patients with MDS showing that normocytosis was an independent adverse prognostic factor for patients with low blast (<5%) MDS, even when tested against clinical, laboratory, and mutation variables.5 The strong correlation of macrocytosis with higher OS probably reflects a more benign phenotype of patients with macrocytosis. The correlation of macrocytosis with erythroid dysplasia may offer a lead to explain this association, probably suggesting that macrocytes derive from erythroblasts surviving the apoptotic processes, implying that less apoptosis, hence more effective erythropoiesis, may lead to more pronounced macrocytosis, while the maturation arrest that accompanies the leukemic phenotype is correlated with less macrocytosis. Understanding the modulators of enuclation and organelle clearance during erythropoiesis may elucidate the pathogenesis and prognostic significance of dyserythropoiesis. In patients with poor cytogenetic features, macrocytosis retained its significance as an independent prognostic factor of a longer OS, and this is in accordance with the results of a study on 164 patients with MDS and abnormal karyotypes, where macrocytosis was independently correlated with a longer OS.6 No further reports on the prognostic role of MCV/macrocytosis in MDS were identified in the literature. The strength of the present study relies on the large number of well-characterized patients with MDS, permitting the identification of the prevalence of macrocytosis in MDS as well as its prognostic significance. Moreover, an effort to exclude patients with known causes of microcytosis/macrocytosis (such as iron deficiency, beta thalassemia trait, and megaloblastic anemia) was made to avoid any confounding factors, but factors such as alcohol consumption and medications, as well as acquired alpha-thalassemia in MDS were not addressed. Moreover, the lack of molecular data in the registry is another limitation of the analysis. A potential limitation of the study is that it comprises a preselected population of patients eventually treated with 5-azacytidine, although these patients were not selected based on their prognostic or any other characteristics. In conclusion, macrocytosis, evident in about a third of patients with MDS, appears to be a significant independent prognostic factor for a steadier clinical course, longer time from diagnosis to treatment, and a higher OS in patients with MDS. Further validation of these results may prompt the inclusion of macrocytosis in the available risk stratification systems, to help patient selection for treatment and refine prognostic categorization. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request. Table S1. Baseline patient characteristics Table S2. Characteristics of patients with and without macrocytosis. Table S3. Cox Regression analysis for overall survival with several models including macrocytosis along with other variables that proved to be statistically significant in univariate analysis. (A) Whole cohort. Model comprising two variables: macrocytosis (MCV >100 fL) and IPSS category (higher vs. lower). (B) Whole cohort. Model comprising two variables: macrocytosis (MCV >100 fL) and thrombocytopenia (platelet count <100 × 109/L). (C) Lower risk patients. Model comprising three variables: macrocytosis (MCV >100 fL), absence of neutropenia (neutrophil count over 1.5 × 109/L) and low bone marrow blast count (≤1%). (D) Lower-risk patients. Model comprising two variables: macrocytosis (MCV >100 fL) and IPSS category (low vs. intermediate 1). (E) Complex karyotype group. Model comprising two variables: macrocytosis (MCV >100 fL) and IPSS category (low vs. intermediate 1). CI, confidence intervals; IPSS, international prognostic scoring system; MCV, mean corpuscular volume Table S4. Cytogenetic data of patients with and without macrocytosis. Data refer to the most common cytogenetic abnormalities, while less common abnormalities (found in <10 patients) are not shown. The columns of multivariate analysis show the results of Cox Regression analysis for overall survival using models comprising macrocytosis and each of the individual cytogenetic abnormalities. The distribution of patients in the different 2016 WHO-defined categories for MDS is also shown. The hazard ratio (HR) and the p value refer both to macrocytosis. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.